I thought RDR's zombie mod would be a bridge too far but - when you just take it at face value (as an alternative, fun plot that totally changes both the mood and the gameplay of the original) - it's really, really well done.

Not played DR2 yet but Case Zero seemed fun. Only problem for me is I'm very much a fan of the runner zombies - and while I'm aware that they're considered sacrilegious by many, I can walk past two hundred zombies in DR without being touched. Try and walk past one in Left 4 Dead without shooting it. Doesn't end well. You need the terror of knowing you can't run or hide (a problem DR has, and a problem I thought RDR would have until I saw how fast they can move), otherwise what's the point?